Method of burning pulverized fuel



July 3, 1923.

J. E. MUHLFELD ET AL METHOD OF BURNING FULVERIPTED FUEL inal Filed Feb. 5, 1918 INVENTORS U NIT JOHN E. MUHLFELD, 0F SCARSDALE, AND VIRGI NIUS Z. CARACRISTI, OF BRONXVILLE, NEW YORK, ASSIGNORS TO LOCOMOTIVE'PULVERIZED FUEL COMPANY, OF NEW YORK, N. Y., A CORPORATION OF DELAWARE.

METHOD OF BURNING PULVERIZED FUEL.

Original application filed February 5, 1918, Serial No. 215,428. Divided and this application filed April of Westchester and State of New York, re-

spectively, have invented certain new and useful Improvements in Methods of Burning Pulverized Fuel, of which the following is a specification.

This invention relates to improvements in methods of burning pulverized fuel, such as coal. and it is a division of our copending application Serial No. 215,428. filed February 5. 1918, issued as Patent No. 1,441,703, January 9, 1923.

It is an object of the-invention to provide an improved method of feedingand mixing the fuel with air. tothe end that the greatest efficiency is obtained from the furnace. 1

Another of the primary objects of our invention is to burn the pulverized fuel in such manner as to obtain what we term stream line combustion in order to promote efliciency by securing superior and more complete combustion and other advanta e's.

More specifically stated, our invention contemplates the introduction of the fuel. or a mixture of the fuel and air, and the admission of a supporter of combustion, such as air, in such manner as not to destroy stream line combustion.

Another object of our invention is to ad init and burn the fuel in the'presence of an embracing or surrounding envelope of columns of air or some other suitable supporter of combustion.

iThe foregoing, together with such other objects as may hereinafter appear. we obtain by means of apparatus, ,the preferred embodiments of. which we have illustrated in the accompanying drawings, wherein Figure 1 is a section through a portion of a furnace adapted for the carrying out of our improved method; Figure 2 is a front elevation of the burner mechanism shown in Figure l; and Figure 3 is a sec-.- tion taken on the line 3--3 of Figure 2 but drawn on an enlarged scale.

Serial No. 464,849.

Heretofore in this art it has been customary to forcibly inject the fuel, or mixture of the "fuel and air, and to inject additional air, for

the reason that it was assumed that the more violent and intimate the mixture of the fuel' combustion chamber and may indeed secure i the intimate admixture sought. but at the expense of mixing the incoming fresh air with the gases of combustion and with othei air the oxygen of which has been Wholly or partially consumed. The incoming air, therefore, may be said to be diluted with the previously admitted airand other gases to form a mixture low in oxygen.

Furthermore, the violent and forcible admission 'of the fuel and air or both, results in more or less forcible impingement of the flames on the walls of the furnace and causes the formation of slag, which hitherto has been a more or less insuperable obstacle to the successful generation of steam by pulverized fuel burning equipment. I

\Ve have discovered that far more efiicient results are obtained and the objectionable features of the old practice obviated, if. in-. stead of forcibly injecting the fuel or the air or both, they be introduced less forcibly and more or less gently, as will further ap pear, in such manner that the air forms an envelope surrounding or embracing the burning column or stream of fuel, such envelope in general following a stream line paralleling the stream line of the burning fuel. We have discovered that the envelope of relatively cold air admittedwill naturally follow the stream line of the burning fuel, as just above set forth, in the absence of the violent agitation hereinbefore mentioned. The foregoing will more clearly appear from description of the furnace shown in the drawings and its operation.

Referring now to the drawings, it will be seen that the furnaceA has a relatively deep combustion chamber 7 which has a lateral extension 8 which may be termed an admission chamber. Where thepractical limitations are such as to prohibit the use of as deep a combustion chamber as is desirable, we locate the bottom wall. 9 on the admission chamber well above the bottom wall 10 of the combustion chamber. for reasons which will further appear. The fuel is preferably admitted vertically downward into the ad mission chamber through the pipes 11. preferably gently. The pipe 11 preferably terminates above the lower end of the burner casting 1; and such casting is constructed so as to provide a channel 13 about the lower end of the pipe 11. and preferably terminating substantially in the same plane. This channel 13 is open to the atmosphere so that air may be induced therein to mix with and surround the fuel discharged from the pipe 11. If desired. additional and jet air may be admitted to the pipe 11 through pipe 11 for induction. or a mixture of fuel and air may be supplied in the first instance to the pipe 11. 4

The casting 12 is also so arranged as to provide three chambers or channels exterior of the channel 13 namely. a channel 14 on each of two opposite sides of the incoming fuel and air and a third channel 15 on the side away from the combustion chamber. These channels 14: and 15 are also open to the atmosphere so that air may be induced therein and. therefore. travel at lower velocity than the fuel. By ,this arrangement the incoming fuel and air discharged from the pipe 11 and channel 13 are partially surrounded or embraced by the columns of air induced into the admission chamber through the channels 14 and 15 on the three sides away from the draft. The draft. which it will be understood, is induced by the usual stack or other. equivalent means. therefore. acts more or less directly upon the incoming fuel or mixture of fuel and air and the fuel follows a stream line generally indicated by the upper arrows. while the surrounding and embracing columns of air follow the same general stream line. enveloping the burning stream of fuel. The lighter particles of fuel are. for the most part. entirely consumed in this stream of burning fuel the necessary oxygen to support the com-',

bustion thereof being "derived either from the air admitted with the fuel or from the air omitted to the channel '13 or both and possibly partly from the surrounding envelope. while the heavier particles which. because of their size. require a larger amountof oxygen. gravitate out of the stream of burning fuel proper into the surrounding columns of air where the additional oxygen required for their combustion is derived. Any additional air that may be required to supplement the columns of air admitted through the burner, may be supplied by one or more inlets 16 in walls of the admission chamber and in some cases through the doors16 and 21 such air also being induced at relatively lower velocity than'the fuel and mingling with and generally following the stream line of the embracing envelope. The number of the inlets 16 depends upon the width of the furnace and the rate of combustion required.

It will be seen that the more or less gentle introduction of the fuel and air compared with the forcible injection of the same heretofore commonly practiced in the art. preserves the stream line effect of both the burning fuel and the air admitted thereabout, and the tire presents the appearance of a relatively large body of flame from which tongues of flame shoot downwardly and outwardly into the envelope, such tongues of flame being formed by the combustion of the heavier particles of fuel gravitating out of the stream of the burning lighter particles of fuel. Thus very efficient and practically complete combustion is obtained and in addition thereto. other advantages follow, such as the greater life of the walls of the furnace, which results from the fact that there is no forcible impingement of the flames on the walls such as would cause the walls to run. Furthermore. if the envelope of surrounding air be of sumcient depth. a neutral or cooling zone is provided through which the precipitating ash is cooled below slag forming temperature and the deposit on the floor of the furnace is in a more or less flocculent condition which permits of its ready removal. in this connec= tion. it will be understood that a great portion of the ash is carried out the stack by the draft.

As before indicated. if it is impossible to provide a furnace of sufficient depth to secure the desired results with respect to the prevention of the formation of slag. the fioor S of the admissionchamber is located above the floor 10 of the combustion chamber so as to assist the draft in shortening the downward length of travel of the fuel. which has the efl'ect of providing a neutral zone below the zone of combustion. roughly indicated at 17. The door 21 is provided for the removal of the ash. and the door 16" for the renewal of the floor 9 of the admission ehamher. It. will be understood that the air inlet pipes and channels may be controlled by damper mechanism 18 of any preferred character.

'We have described the burner mechanism as a single burner. but it will be readily understood that a plurality of burners may be employed, such as shown in Figures 2 and El.

The front wall is protected by the air induced into the space between the descending portion of the fuel and flame stream and the front wall.

The admission of part of the air for con bustion with the coal and the balance of the perature in contradistinction to a short clear flame which would have a localized zone o't' extreme temperature destructive of the brick work and productive of the formation of slag by virtue of its relatively much higher radiation. The shape of the combustion chamber and the manner of coal admission gives the longer flame travel needed for the softer type of flame stream. However, the combustion is very eflicient and rapid because the method of admitting the coal and the air takes cognizance of the fact that combustion itself'is progressive and that there is movement of the flames through the combustion space. The descending portion of the fuel and flame stream and the ascending portion thereof are close'so that the former is subjected to the heat of the latter.

We claim:

1. The process of burning pulverized coal in a combustion chamber having an outlet in an upper part thereof which consists in admitting the fuel in a downward direction adjacent a wall thereof. in substantially completing combustion within the chamber.

and in drawing off the gaseous products of.

combustion through said outlet at such a rate as to produce stream line combustion of the fuel with a reverting U-shaped fuel and flame stream in which the descending portion is subjected to the heat of the ascending portion.

2. The process of burning pulverized coal in a combustion chamber having an outlet in an upper part thereof which consists in admitting the fuel in a downward direction adjacent a wall thereof. in drawing off the gaseous products of combustion through said outlet at such a rate as to produce stream line combustion of the fuel with a reverting U-shapcd fuel and flame stream in which the descending-portion is subjected to the heat of the ascending portion. and in supplying air for combustion to the stream at succes-' sive points along the descending portion thereof. whereby combustion is substantially completed within the chamber.

3. The process of burning pulverized coal in a combustion chamber having an outlet in an upper part thereof which consists in admitting the fuel in a downward direction adjacent a wall thereof, in drawing off the gaseous products of combustion through said outlet at such a rate as to produce stream line combustion of the fuel with a reverting U-shaped fuel and flame stream in which the dcscending portion is subjected to the heat of the ascending portion. and in supplying air for combustion to the stream at succesive points along the descending portion thereof by inducing said air into the chamber, whereby combustion issubstantially completed within the chamber.

. 4. The process of burning pulverized coal in a combustion chamber having an outlet in an upper part thereof which consists in.

admitting the fuel in a downward direction adjacent a wall thereof. in drawing off'the gaseous products of combustion through said outlet at such a rate as to produce stream line combustion of the fuel with a. reverting U-shaped fuel and flame stream in which the descending portion is subjected to the heat of the ascending portion, and in supplying air for combustion to the stream at successive points along the. descending portion thereof by inducing said air into the chamber, into the space between the stream and the said wall, whereby combustion is substantially completed within the chamber.

5. The process of burning pulverized coal in a combustion chamber having an outlet in an upper part thereof which consists in admitting the fuel in a downward direct-ion adjacent a wall thereof, in drawing off the gaseous products of combustion through said outlet at such a rate as to produce stream line combustion of the fuel with a reverting U-shaped fuel and flame stream in which the descending portion is subjected to the heat of the ascending portion. and in supplying air for combustion to the desccnding portion of said stream by inducing said air into the chamber, into the space hetween'the stream and the said wall, in a direction transverse to the line of movement of the descending portion of the flame, whereby combustion is substantially completed in the combustion chamber.

6. The process of burning pulverized coal in a combustion chamber having an outlet in an upper part thereof which consists in admitting the fuel in a downward direction adjacent a wall thereof. in drawing off the gaseous products of combustion through said outlet at such a rate. as to produce stream line combustion of the fuel with a reverting U-shaped fuel and flame stream in which the descending portion is subjected to the heat of the ascending portion. and in supplying air for combustion to the descending portion of said stream by inducing said air into the chamber, into the space between the stream and the said wall. in a direction transverse to the line of movement of the descending portion of the flame. the fuel being introduced at higher-velocity than that of the said air. whereby combustion is substantially completed within the (OllllJllSf-lOIl chamber.

T. The process of burning pulverized fuel in a combustion chamber having an outlet in the upper part thereof which consists in admitting'the fuel in a downward direc-.

tion adjacent a wall thereof, in admitting 'and such combustion air mingle and burn in stream line combustion with a reverting U-shaped fuel and flame stream, the descending portion of which is subjected to the heat of the ascending portion. and such that combustion is substantially completed within said chamber.

8. The process of burning pulverized fuel in a combustion chamber having an outlet in the upper part thereof which consists in admitting the fuel in a downward direction adjacent a wall thereof, in admitting air for combustion and in drawing off the gaseous products of combustion through said outlet; with velocities of the fuel. the air. and the waste gases such that the fuel and such combustion air mingle and burn in stream line combustion with av reverting U-shaped fuel and flame stream. the descending portion of which is subject to the heat of the ascending portion. and such that combustion is substantially completed within said chamber, part ofsaid air being admitted at the point of fuel admission and part through the said wall therebelow but well above the bottom of the chamber.

9. The process of burning pulverized fuel in a combustion chamber having an outlet in the upper part thereof which. consists in admitting the fuel in a downward dire-c tion adjacent a wall thereof, in admitting air for combustion. in drawing off the gaseous products of combustion.through said outlet. the coal being introduced at higher velocity than that of the waste gas outlet flow and the air being introduced adjacent the descending coal but at less velocity than that of the. entering coal. and all velocities being such that the fuel and air intermix and burn in stream line combustion with a. reverting U-shaped fuel and flame stream. the descending portion of 10. The process which consists in admitting. into a combustion chamber having an outlet in an upper portion and a place at the bottom for deposit of refuse of combustion pulverized coal at one side of the chamber-and adjacent to but spacedaway from a wall thereof and in a downward direction in supplying combustion air for igni tion of the descending fuel, and in drawing off the gaseous products of combustion at such a rate and in such a direction that the descending fuel and flame stream is turned inwardly into the chamber away from such wall and then upwardly in U-shape. with the base or bend of the stream well above the point of deposit, and that substantial stream line combustion is produced,

with completion of combustion within the chamber.

11. The process which consists in admitting pulverized fuel, in a combustion chamber having an outlet in an upper part there: of. in a downward direction adjacent a wall of the chamber and burning it 'with a re,- verting U-shaped fuel and flame stream, the descending portion of which is subject to the heat of the ascending portion, and in admitting a stream of air bordering the descending portion on the convex side of the fuel and flame stream.

12. The process which-consists in admitting pulverized fuel. in a combustion chamher having an outlet in an upper part thereof. in a downward direction adjacent a wall of the chamber and burning it with a reverting U-shaped fuel and flame stream, the descending portion of which is subject to the heat of the ascending portion, and in maintaining a substantial body of relatively cool= air between the descending portion and, such wall.

13. The process which consists in admitting pulverized fuel, in a combustion chamber having an outlet in an upper part thereof in a downward direction adjacent a wall of the chamber and burning it with a reverting U-shaped fuel and flame stream, the descending portion of which is subject to the heat of the ascending portion, and in maintaining a substantial body of relative ly cool air between the descending portion and such wall, such air being introduced through the said wall.

14. The process which consists in-admitting pulverized coal, in a combustion chamher having an outlet in an upper part thereof, in a downward direction adjacent a wall of the chamber and burning it with a reverting U-shaped fuel and flame stream. the descending portion of which is subjected to the heat of the ascending portion, and in maintaining a substantial body relatively cool air between the descending portion and such wall. such air being introduced adjacent the entering fuel.

15. The process which consists in admitting pulverized fuel, in a combustion chamher having an outlet in an upper part thereof. in a downward direction adjacent awall' of the chamber and burning it'with a reverting U-shaped fuel and flame stream, and in admitting air for combustion near the entering fuel but at lower velocity than that of the fuel so that the fuel flows past or through a slower moving body of air.

16. The process which consists in admitting pulverized fuel, in a combustion chamher having an outlet in an upper part thereof. in a downward direction adjacent a wall.

of the chamber and burning it with a re- 7 body of air.

17. The process which consists in admitting pulverized fuel, in a combustion chamber having an outlet in an upper part there of, in a downward direction adjacent a wall of the chamber and burning it with a reverting U-shaped fuel and flame stream, and in maintaining a stream of air bordering the fuel and flame stream on the convex side thereof into which heavier unconsumed or partially'consumed particles of coal gravitating out of the main body of flame pass and are consumed.

18. The process of burning pulverized coal in a combustion chamber having an outlet which consists in admitting the fuel and in drawing a trough-shaped body of air into the chamber, the base and sides whereof border the fuel and flame stream and are intermediate said stream and the JOHN E. MUHLFELD. VIRGINIUS z. CARACRISTI. 

